Battery pack and method for manufacturing battery pack

ABSTRACT

A battery pack includes a plurality of battery cells each including a laminate film casing from which positive and negative electrode lead tabs are led out in a same direction, and a coupling assisting member that includes a conductive plate member fixing portion that fixes a conductive plate member having first and second main surfaces, and first and second slit portions provided on the first and second main surface sides of the conductive plate member, respectively. Either of the positive and negative lead tabs of one battery cell is inserted through the first slit portion and conductively connected to the first main surface. A lead tab of a battery cell adjoining one battery cell and having a polarity different from that of the lead tab of the one battery cell, is inserted through the second slit portion and conductively connected to the second main surface.

This application is a National Stage of International Application No.PCT/JP2017/034874 filed Sep. 27, 2017, claiming priority based onJapanese Patent Application No. 2017-042977 filed Mar. 7, 2017.

TECHNICAL FIELD

The present invention relates to a battery pack accommodating a batterycoupling structure formed by connecting battery cells such as lithiumion secondary batteries, and a method for manufacturing the same.

BACKGROUND ART

Lithium ion batteries having high energy density and light weight hasbeen increasingly used as battery cells mounted in a battery packcontainer. Laminate batteries using a laminate film made of a flexiblealuminum sheet of several tens to several hundreds of micrometers inthickness and a resin as a casing are particularly light in weight andare expected to be used for various applications.

A battery using a laminate film casing is configured so that anelectrode stack formed by stacking a plurality of positive electrodesand a plurality of negative electrodes via separators and an electrolytesolution with which the electrode stack is impregnated are accommodatedinside the laminate film casing, and the rims of the laminate filmcasing are heat sealed.

Battery cells using a flexible laminate film as the casing excel interms of weight reduction but have a problem of low strength andvulnerability to external impact, compared to square batteries andcylindrical batteries having a thick, large metal plate casing.

If a battery pack is connected to a device that needs a large batterycapacity and the like, a plurality of battery cells inevitably needs tobe connected for use. If a plurality of laminate type battery cells isaccommodated in a battery pack, the battery cells are either stacked ina stacking direction or arranged in a row in parallel with the insidesurface of the outer case.

For example, Patent Document 1 (WO/2012/131802) discloses a battery packaccommodating a battery coupling structure in which unit batteries 100are stacked and connected by a substrate 300. Patent Document 1:WO/2012/131802

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Attempts have been made in recent years to use flying objects such as adrone in business and other fields. Since a battery pack mounted on aflying object needs to have high energy density and light weight, itmakes sense to use a battery pack including a battery cell with alaminate film casing.

On the other hand, if the battery pack to be mounted on a flying objectincludes a plurality of battery cells connected to obtain high output,the connections need to have high resistance against impact and highresistance against vibrations.

However, battery packs according to the conventional technique have hada problem of fragility to impact and vibrations since mechanical fixingmeans such as bolts are used to electrically connect the lead tabs ofthe battery cells.

Conventional battery packs have also had a problem of increased weightsince bolts are used to electrically connect the lead tabs of thebattery cells.

In a conventional battery pack, the lead tabs of the battery cells arebent at 90° when the lead tabs are electrically connected to each other.There has thus been a problem of a drop in the performance of thebattery cells because such bending applies an external force to thebattery cells themselves.

The conventional technique has also had a problem of complicatedmanufacturing steps and high cost because electrically connecting thelead tabs as described above needs the steps of bending the lead tabs at90°, stacking and positioning the battery cells one by one, andfastening the same by bolts.

Means for Solving the Problems

The present invention is intended to solve the foregoing problems. Abattery pack according to the present invention is a battery packincluding a stack of a plurality of battery cells that each include apositive electrode lead tab and a negative electrode lead tab led out ofa laminate film casing in a same direction, and a coupling assistingmember that assists in electrically connecting adjoining battery cells,wherein: the coupling assisting member includes a conductive platemember fixing portion that fixes a conductive plate member having afirst main surface and a second main surface in a front-to-backrelationship with the first main surface, a first slit portion providedon the first main surface side of the conductive plate member, and asecond slit portion provided on the second main surface side of theconductive plate member; either one of the positive and negative leadtabs of one battery cell is inserted through the first slit portion andconductively connected to the first main surface of the conductive platemember; and a lead tab of a battery cell adjoining the one battery cell,the lead tab having a polarity different from that of the lead tab ofthe one battery cell, is inserted through the second slit portion andconductively connected to the second main surface of the conductiveplate member.

In the battery pack according to the present invention, the couplingassisting member includes a guide plate that, when a lead tab of abattery cell is inserted through the first slit portion or the secondslit portion, guides an end of the lead tab toward the first slitportion or the second slit portion.

In the battery pack according to the present invention, a position whereeither one of the positive and negative lead tabs of the one batterycell is inserted through the first slit portion and conductivelyconnected to the first main surface of the conductive plate member and aposition where the lead tab of the battery cell adjoining the onebattery cell, the lead tab having the polarity different from that ofthe lead tab of the one battery cell, is inserted through the secondslit portion and conductively connected to the second main surface ofthe conductive plate member do not overlap as seen in a thicknessdirection of the conductive plate member.

In the battery pack according to the present invention, the conductiveplate member fixing portion of the coupling assisting member includes aconductive plate member sandwiching portion that sandwiches theconductive plate member.

In the battery pack according to the present invention, the conductiveplate member fixing portion of the coupling assisting member includes aconductive plate member latch portion that latches the conductive platemember.

In the battery pack according to the present invention, a notch for theconductive plate member latch portion to be engaged with is formed inthe conductive plate member.

In the battery pack according to the present invention, a terminal pieceis formed on the conductive plate member.

In the battery pack according to the present invention, a substratehaving a through hole for the terminal piece to run through is placed onthe coupling assisting member.

A method for manufacturing a battery pack according to the presentinvention is a method for manufacturing a battery pack including a stackof a plurality of battery cells that each include a positive electrodelead tab and a negative electrode lead tab led out of a laminate filmcasing in a same direction, and a coupling assisting member that assistsin electrically connecting adjoining battery cells, the couplingassisting member including a conductive plate member fixing portion thatfixes a conductive plate member having a first main surface and a secondmain surface in a front-to-back relationship with the first mainsurface, a first slit portion provided on the first main surface side ofthe conductive plate member, and a second slit portion provided on thesecond main surface side of the conductive plate member, the methodincluding the steps of: inserting either one of the positive andnegative lead tabs of one battery cell into the first slit portion andconductively connecting the lead tab to the first main surface of theconductive plate member; and inserting a lead tab of a battery celladjoining the one battery cell, the lead tab having a polarity differentfrom that of the lead tab of the one battery cell, into the second slitportion and conductively connecting the lead tab to the second mainsurface of the conductive plate member.

Advantageous Effects of the Invention

According to the battery pack of the present invention, a battery packhaving light weight, resistant to mechanical vibrations and impact, andhaving excellent manufacturability can be provided.

According to the method for manufacturing a battery pack of the presentinvention, a battery pack having light weight and resistant tomechanical vibrations and impact can be easily manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a battery cell 100 used in a battery pack700 according to an embodiment of the present invention.

FIG. 2 is a diagram showing a reinforcing member 200 used in the batterypack 700 according to the embodiment of the present invention.

FIG. 3 is a diagram showing a manufacturing step of the battery pack 700according to the embodiment of the present invention, a diagram showingthe order of stacking of battery cells 100 and reinforcing members 200.

FIG. 4 is a diagram showing a stack of battery cells 100 and reinforcingmembers 200.

FIG. 5 is a diagram showing a coupling assisting member 300 used in thebattery pack 700 according to the embodiment of the present invention.

FIG. 6 is an exploded perspective view of the coupling assisting member300 used in the battery pack 700 according to the embodiment of thepresent invention.

FIG. 7 is a diagram showing a manufacturing step of the battery pack 700according to the embodiment of the present invention.

FIGS. 8(A)-8(C) are schematic diagrams showing how lead tabs of batterycells 100 are guided by the coupling assisting member 300.

FIG. 9 is a diagram showing a manufacturing step of the battery pack 700according to the embodiment of the present invention.

FIGS. 10(A) and 10(B) are diagrams for describing the order of weldingof lead tabs and the coupling assisting member 300.

FIGS. 11(A) and 11(B) are diagrams for describing the order of weldingof the lead tabs and the coupling assisting member 300 by an ultrasonicwelding apparatus.

FIG. 12 is a diagram showing a battery coupling structure 500 used inthe battery pack 700 according to the embodiment of the presentinvention.

FIG. 13 is an exploded perspective view of the battery couplingstructure 500 used in the battery pack 700 according to the embodimentof the present invention.

FIG. 14 is a front view of the battery coupling structure 500.

FIG. 15 is a sectional view taken along line A-A shown in FIG. 14.

FIG. 16 is a side view of the battery coupling structure 500.

FIG. 17 is a sectional view taken along line B-B shown in FIG. 16.

FIG. 18 is a schematic diagram showing an internal structure of abattery cell 100.

FIG. 19 is a schematic diagram for describing an effect of vibrations inwelding a lead tab to the coupling assisting member 300 on the internalstructure of the battery cell 100.

FIG. 20 is a chart showing a relationship between a frequency ratio [u]and a vibration transmission ratio [τ].

FIG. 21 is a diagram for describing a concept of changing the vibrationtransmission ratio by providing a vibration transmission ratio changingbend 150 on the lead tab.

FIG. 22 is a diagram showing the battery pack 700 according to theembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below withreference to the drawings. FIG. 1 is a diagram showing a battery cell100 used in a battery pack 700 according to the embodiment of thepresent invention. A lithium ion secondary unit battery which is chargedand discharged by movement of lithium ions between negative and positiveelectrodes is used as the battery cell 100.

A battery main body unit 110 of the battery cell 100 is configured sothat an electrode stack including a plurality of sheet-like positiveelectrodes and a plurality of sheet-like negative electrodes stacked viaseparators and an electrolyte solution (neither of which is shown in thediagram) are accommodated in a laminate film casing 103 having arectangular shape in a plan view. A positive electrode lead tab 120 anda negative electrode lead tab 130 are led out of a first end portion 111of the battery main body unit 110.

The positive electrode lead tab 120 and the negative electrode lead tab130 both have a flat plate shape and are connected to the sheet-likepositive electrodes and the sheet-like negative electrodes,respectively, inside the laminate film casing 103 either directly or vialead members or the like. The laminate film casing 103 is made of ametal laminate film having a heat sealing resin layer on a surfacefalling on the inner side of the battery. More specifically, forexample, two metal laminate films are stacked to constitute the laminatefilm casing 103. With the electrode stack including the sheet-likepositive electrodes, the sheet-like negative electrodes, and theseparators and the electrolyte solution accommodated inside, an outerperiphery (the first end portion 111, a second end portion 112, and twoside end portions 113) of the laminate film casing is thermally sealedto hermetically close the interior.

As employed herein, metal pieces led out of the battery main body unit110 including the laminate film casing 103, like the positive electrodelead tab 120 and the negative electrode lead tab 130, will be referredto as “lead tabs”. The sheet-like positive electrodes and the sheet-likenegative electrodes stacked inside the laminate film casing 103 via theseparators, the electrolyte solution, and the like will be referred toas “electrodes”.

Aside from one constituted by stacking a plurality of sheet-likepositive electrodes and a plurality of sheet-like negative electrodesvia separators as described above, electrode stacks may also include oneconstituted by stacking a sheet-like positive electrode and a sheet-likenegative electrode via a separator, and winding and compressing thesame.

In the battery cell 100 described above, aluminum or an aluminum alloyis typically used as the material of the positive electrode lead tab120. Nickel, a material formed by plating another metal with nickel(nickel-plated material, such as nickel-plated copper), or another metalcladded with nickel (nickel-cladded material, such as nickel-claddedcopper) is typically used as the material of the negative electrode leadtab 130. In other words, the battery cell 100 includes a positiveelectrode lead tab 120 containing aluminum and a negative electrode leadtab 130 containing nickel. In the present embodiment, a positiveelectrode lead tab 120 made of aluminum and a negative electrode leadtab 130 made of nickel are used.

In the battery cell 100 used in the battery pack 700 according to theinvention, a rectangular notch 125 is formed in the positive electrodelead tab 120 and a rectangular notch 135 in the negative electrode leadtab 130 in advance for the sake of convenience in manufacturing thebattery pack 700. The role of the notches in the positive electrode leadtab 120 and the negative electrode lead tab 130 in the manufacturingsteps will be described later.

Next, a reinforcing member 200 used in stacking a plurality of batterycells 100 will be described. FIG. 2 is a diagram showing the reinforcingmember 200 used in the battery pack 700 according to the embodiment ofthe present invention.

The reinforcing member 200 is a member made of synthetic resin and hasthe role of reinforcing a stack of battery cells 100 in stacking aplurality of battery cells 100.

The reinforcing member 200 includes a flat plate portion 210 ofsubstantially rectangular shape which makes contact with an electrodestacking region 105 of the laminate film casing 103 of a battery cell100 when battery cells 100 are stacked.

Rim portions 220 extending in a direction perpendicular to the mainsurface directions of the flat plate portion 210 are provided on threesides of the flat plate portion 210 of substantially rectangular shape.Handle portions 225 extending further from the rim portions 220 areprovided on two opposed sides of the flat plate portion 210 ofsubstantially rectangular shape. The handle portions 225 serve ashandles for improving the handling of the stack of battery cells 100.For that purpose, a periodic texture pattern is formed on the handleportions 225 so that appropriate friction can be produced. The handleportions 225 can also be used when a battery coupling structure 500 or abattery pack 700 is completed.

The reinforcing member 200 includes two protrusions 240 extending fromthe two opposed sides of the flat plate portion 210 of substantiallyrectangular shape. The protrusions 240 are formed on the reinforcingmember 200 so that when a stack of battery cells 100 is formed by usingthe reinforcing member 200, the protrusions 240 protrude in the samedirection as that in which the positive electrode lead tabs 120 and thenegative electrode lead tabs 130 of the battery cells 100 are led out.The protrusions 240 are configured to be engaged with recessed guides340 that are guide portions of a coupling assisting member 300 to bedescribed later. Latch pieces 245 are provided on the end side of theprotrusions 240. The latch pieces 245 are used to securely fix thereinforcing member 200 to the coupling assisting member 300.

Next, a method for stacking a plurality of battery cells 100 configuredas described above and electrically connecting the adjoining batterycells 100 to form a battery coupling structure 500, and therebymanufacturing a battery pack 700 will be described.

FIG. 3 is a diagram showing a manufacturing step of the battery pack 700according to the embodiment of the present invention, a diagram showingthe order of stacking of battery cells 100 and reinforcing members 200.FIG. 4 is a diagram showing a stack of battery cells 100 and reinforcingmembers 200.

The battery cells 100 and the reinforcing members 200 are stacked byusing a not-shown double-sided adhesive tape so that the members arefirmly bonded to each other. In the present embodiment, a batterycoupling structure 500 including six battery cells 100 connected inseries is intended to be formed. However, in the battery pack 700according to the present invention, the number of battery cells 100connected in series may be arbitrary.

In the present embodiment, the stack is formed to include two batterycells 100, a reinforcing member 200, two battery cells 100, areinforcing member 200, and two battery cells 100 in order as shown inthe diagram.

Attention will be focused on the portion encircled by a dot-dashed linein FIG. 4. The flat plate portions 210 of the reinforcing members 200interposed between the battery cells 100 are provided to cover thelaminate film casings 103 at the first end portions 111 of the batterycells 100 when seen in the stacking direction of the battery cells 100.

This can appropriately protect the relatively-fragile first end portion111 side of the battery cells 100 from which the positive electrode leadtabs 120 and the negative electrode lead tabs 130 are led out.

Next, the coupling assisting member 300 which assists in electricallyconnecting the adjoining battery cells 100 will be described. FIG. 5 isa diagram showing the coupling assisting member 300 used in the batterypack 700 according to the embodiment of the present invention. FIG. 6 isan exploded perspective view of the coupling assisting member 300 usedin the battery pack 700 according to the embodiment of the presentinvention.

A frame member 310 of substantially rectangular shape, made of syntheticresin or the like is used as a chief base structure of the couplingassisting member 300. Conductive plate members 350 to be used forwelding with the lead tabs of the battery cells 100 are implanted in theframe member 310. A substrate 390 is placed on the frame member 310. Theconductive plate members 350 can be made of a metal material such ascopper.

In the present embodiment, the number of conductive plate members 350fixed to the frame member 310 is seven. The number can be changed asappropriate based on the number of battery cells 100 to be connected inseries.

The two conductive plate members 350 arranged at opposite ends of theframe member 310 are each welded with either the positive electrode leadtab 120 or the negative electrode lead tab 130 at the end side of thebattery cells 100 connected in series. The conductive plate members 350other than the two conductive plate members 350 are each welded with,for example, both the positive electrode lead tab 120 of a battery cell100 and the negative electrode lead tab 130 of a battery cell 100adjoining the battery cell 100. In other words, the conductive platemembers 350 other than the two conductive plate members 350 are eachwelded with two lead tabs including either one of the positive andnegative lead tabs of one battery cell 100 and a lead tab of a batterycell 100 adjoining the one battery cell 100, the lead tab having apolarity different from that of the lead tab of the one battery cell100.

Conductive plate member fixing portions 320 that are a structure forfixing the conductive plate members 350 are provided inside the framemember 310 of substantially rectangular shape. The conductive platemember fixing portions 320 for fixing the conductive plate members 350to the frame member 310 include two types of portions, namely,conductive plate member sandwiching portions 322 and conductive platemember latch portions 325.

The conductive plate member sandwiching portions 322 are slit-likeportions capable of sandwiching the conductive plate members 350. Theslits of the conductive plate member sandwiching portions 322 have awidth approximately the same as the thickness of the conductive platemembers 350. The conductive plate member sandwiching portions 322 cansandwich the conductive plate members 350.

Conductive plate member latch portions 325 of protruded shape fitting totwo notches 353 formed in the respective conductive plate members 350are formed at positions not visible in FIGS. 5 and 6. The conductiveplate member latch portions 325 can be observed in FIG. 17 which is asectional view of the frame member 310.

A guide plate 330 is provided on the frame member 310 so as tocorrespond to each of the two conductive plate members 350 arranged atthe opposed ends of the frame member 310. Two guide plates 330 areprovided so as to correspond to each of the conductive plate members 350other than the two conductive plate members 350. Predetermined gaps(first slit portions 361 and second slit portions 362) are formedbetween the conductive plate members 350 and the guide plates 330.During manufacturing, the guide plates 330 give an appropriate bend tothe lead tabs of the battery cells 100 and guide the lead tabs into thegaps (first slit portions 361 and second slit portions 362).

The conductive plate members 350 each have a first main surface 351 anda second main surface 352 in a front-to-back relationship with the firstmain surface 351. For example, the positive electrode lead tab 120 of abattery cell 100 is welded to the first main surface 351 of a conductiveplate member 350, and the negative electrode lead tab 130 of anadjoining battery cell 100 is welded to the second main surface 352.

The conductive plate members 350 each have two notches 353 of recessedshape. The notches 353 are configured to fit to the conductive platemember latch portions 325 of protruded shape on the frame member 310.The conductive plate members 350 are thereby fixed to the frame member310. The conductive plate members 350 each have a slit portion 355,which facilitates the conductive plate members 350 bending when thenotches 353 are fitted to the conductive plate member latch portions 325of protruded shape.

Terminal pieces 357 are protruded from the conductive plate members 350.When the substrate 390 is placed on the frame member 310, the terminalpieces 357 of the conductive plate members 350 are inserted throughrespective through holes 393 in the substrate 390.

A metal film wiring pattern (details will be omitted) is formed on thesubstrate 390. For example, the terminal pieces 357 protruding from thethrough holes 393 of the substrate 390 are electrically connected to thewiring pattern by soldering or the like. Power lines 610 of the batterycells 100 connected in series and sense lines 620 for sensing thepotentials of the respective battery cells 100 can thus be drawn outfrom the substrate 390.

Two recessed guides (guide portions) 340 are formed on each of twoopposed sides of the outer periphery of the substantially rectangularframe member 310. The recessed guides 340 engage with the protrusions240 of the reinforcing members 200.

In a battery pack according to the conventional technique, a substratefor electrically connecting the lead tabs of the battery cells and abattery protection member on side surfaces of the stacked battery cellsare configured to be mutually regulated in position via the batterycells. There has thus been a problem that application of impact orvibrations from outside can cause a break in the relatively fragile leadtabs, lowering the reliability of the battery pack.

According to the conventional technique, there has also been a problemof complicated manufacturing steps and high cost because electricallyconnecting the lead tabs as described above needs the steps of bendingthe lead tabs at 90°, stacking and positioning the battery cells one byone, and fastening the same by bolts.

In the battery pack 700 according to the present invention, thereinforcing members 200 for protecting the stacks of a plurality ofbattery cells 100 and the coupling assisting member 300 for electricallyconnecting the plurality of battery cells 100 are configured to be fixedto each other so that the relative position between the reinforcingmembers 200 and the coupling assisting member 300 does not change.

Components for that purpose includes the protrusions 240 of thereinforcing members 200 and the recessed guides 340 formed on the framemember 310 of the coupling assisting member 300. Such components alsoimprove the manufacturability of the battery pack 700.

FIG. 7 is a diagram showing a manufacturing step of the battery pack 700according to the embodiment of the present invention. FIG. 7 shows thestep of inserting the lead tabs led out of the battery cells 100constituting the stack through slit portions formed in the couplingassisting member 300.

To guide the lead tabs of the battery cells 100 into predetermined slitportions, the coupling assisting member 300 is brought closer to thestack of battery cells 100 so that the protrusions 240 of thereinforcing members 200 and the recessed guides 340 formed on the framemember 310 of the coupling assisting member 300 are engaged to regulatethe positional relationship.

If the coupling assisting member 300 is brought closer to the stack ofbattery cells 100 and the insertion of the lead tabs through thepredetermined slit portions is completed, the latch pieces 245 at theend side of the protrusions 240 are engaged with the frame member 310 ofthe coupling assisting member 300. The reinforcing members 200 arethereby fixed to the coupling assisting member 300. This completes theoperation for combining the coupling assisting member 300 and the stackof battery cells 100.

FIG. 9 is a diagram showing a manufacturing step of the battery pack 700according to the embodiment of the present invention. FIG. 9 shows astate where the operation for combining the stack of battery cells 100and the coupling assisting member 300 is completed.

As described above, according to the battery pack 700 of the presentinvention, a highly reliable battery pack 700 having excellentmanufacturability can be provided.

According to the method for manufacturing the battery pack 700 of thepresent invention, a highly reliable battery pack 700 can be easilymanufactured.

By the way, a battery pack according to the conventional technique hashad a problem of fragility to impact and vibrations because mechanicalfixing means such as bolts are used in electrically connecting the leadtabs of the battery cells.

The conventional battery pack has also had a problem of increased weightbecause bolts are used to electrically connect the lead tabs of thebattery cells.

In the conventional battery pack, the lead tabs of the battery cells arebent at 90° when the lead tabs are electrically connected. There hasalso been a problem of a drop in the performance of the battery cellsbecause such bending applies an external force to the battery cellsthemselves.

The conventional technique has also had a problem of complicatedmanufacturing steps and high cost because electrically connecting thelead tabs as described above needs the steps of bending the lead tabs at90°, stacking and positioning the battery cells one by one, andfastening the same by bolts.

The battery pack 700 according to the present invention then solves theforegoing problems of the conventional technique by the use of thecoupling assisting member 300 for electrical connection between thebattery cells 100.

A relationship between the lead tabs of the battery cells 100 and thecoupling assisting member 300 in combining the coupling assisting member300 and the stack of battery cells 100 will initially be described.FIGS. 8(A)-8(C) are schematic diagrams showing how the lead tabs ofbattery cells 100 are guided by the coupling assisting member 300.

For example, focusing attention on the conductive plate member 350encircled by a dot-dashed line in FIG. 9, FIGS. 8(A)-8(C) showconfiguration in the vicinity of the conductive plate member 350 in anextracted manner. Suppose that the left side of the conductive platemember 350 is the first main surface 351 and the right side the secondmain surface 352. The terms “first” and “second” are only intended tomake a distinction between the main surfaces and not to represent anyhierarchy.

The slit portion between the first main surface 351 of the conductiveplate member 350 and the guide plate 330 will be referred to as a firstslit portion 361. The slit portion between the second main surface 352of the conductive plate member 350 and the guide plate 330 will bereferred to as a second slit portion 362.

In FIGS. 8(A)-8(C), the positive electrode lead tab 120 of the leftbattery cell 100 is assumed to be inserted through the first slitportion 361, and the negative electrode lead tab 130 of the adjoiningright battery cell 100 is to be inserted through the second slit portion362. However, the polarities of the lead tabs may be opposite to suchassumption.

FIG. 8A shows a state when the operation for combining the couplingassisting member 300 and the stack of battery cells 100 is started. FIG.8B shows a state where the combining operation is in process. FIG. 8Cshows a state when the combining operation is completed.

As shown in FIG. 8B, in the combining process, the ends of the positiveelectrode lead tab 120 and the negative electrode lead tab 130 makecontact with and are guided along the guide plates 330 toward the firstslit portion 361 and the second slit portion 362, respectively.

As the combining process progresses, the positive electrode lead tab 120and the negative electrode lead tab 130 pass through the first slitportion 361 and the second slit portion 362. The end portions of thepositive electrode lead tab 120 and the negative electrode lead tab 130extend along the first main surface 351 and the second main surface 352of the conductive plate member 350, respectively.

The positive electrode lead tab 120 and the negative electrode lead tab130 form bends (vibration transmission ratio changing bends 150 to bedescribed later) where the lead tabs follow and make contact with theguide plates 330.

As described above, in manufacturing the battery pack 700 according tothe present invention, the guide plates 330 provided on the couplingassisting member 300 facilitate inserting the lead tabs of the batterycells 100 through predetermined slit portions. This improvesmanufacturing efficiency.

Next, a step of welding the positive electrode lead tab 120 and thenegative electrode lead tab 130 inserted through the slit portions asdescribed above to the first main surface 351 and the second mainsurface 352 of the conductive plate member 350, respectively, will bedescribed.

A major characteristic of the battery pack 700 according to the presentinvention is that the lead tabs of the battery cells 100 areelectrically connected without using mechanical fixing means such asbolts which are vulnerable to impact and vibrations and cause anincrease in weight, but by using ultrasonic welding for welding metalmembers to each other by application of ultrasonic vibrations.

In ultrasonic welding, objects to be welded are sandwiched between ananvil 1010 and a horn 1020 of an ultrasonic welding apparatus (entireapparatus is not shown), and the horn 1020 is vibrated by ultrasonicwaves to form a welded portion between the metal interfaces.

In the present example, the positive electrode lead tab 120 is incontact with the first main surface 351 of the conductive plate member350, and the negative electrode lead tab 130 is in contact with thesecond main surface 352. A method of sandwiching the three layers,namely, the positive electrode lead tab 120, the conductive plate member350, and the negative electrode lead tab 130 between the anvil 1010 andthe horn 1020 and forming welds at a time may seem to be capable ofefficiently forming welds. However, such a welding method is not usable,because the conductive plate member 350 has a thickness more than twicethat of the positive electrode lead tab 120 and the negative electrodelead tab 130.

In manufacturing the battery pack 700 according to the presentinvention, a welding method of performing the ultrasonic welding of thepositive electrode lead tab 120 and the conductive plate member 350 andthe ultrasonic welding of the negative electrode lead tab 130 and theconductive plate member 350 independently is then used. Because of usingsuch a welding method, the notch 125 is formed in the positive electrodelead tab 120 and the notch 135 is formed in the negative electrode leadtab 130.

An ultrasonic welding procedure in manufacturing the battery pack 700according to the present invention will be described below withreference to FIGS. 10(A) and (B) and FIGS. 11(A) and 11(B). FIGS. 10(A)and 10(B) are diagrams for describing the order of welding of the leadtabs and the coupling assisting member 300. FIGS. 11(A) and 11(B) arediagrams for describing the order of welding of the lead tabs and thecoupling assisting member 300 by the ultrasonic welding apparatus.Again, description will be given with attention focused on theconductive plate member 350 encircled by a dot-dashed line in FIG. 9.

FIG. 10A is a diagram for describing the welding of the second mainsurface 352 of the conductive plate member 350 and the negativeelectrode lead tab 130. Here, as shown in FIG. 11A, the conductive platemember 350 and the negative electrode lead tab 130 are sandwichedbetween the anvil 1010 and the horn 1020, with the first main surface351 of the conductive plate member 350 in contact with the anvil 1010and the negative electrode lead tab 130 in contact with the horn 1020.The horn 1020 is then vibrated to weld the conductive plate member 350and the negative electrode lead tab 130.

Subsequently, a step of welding the conductive plate member 350 and thepositive electrode lead tab 120 is performed. FIG. 10B is a diagram fordescribing the welding of the first main surface 351 of the conductiveplate member 350 and the positive electrode lead tab 120. Here, as shownin FIG. 11B, the conductive plate member 350 and the positive electrodelead tab 120 are sandwiched between the anvil 1010 and the horn 1020,with the second main surface 352 of the conductive plate member 350 incontact with the anvil 1010 and the positive electrode lead tab 120 incontact with the horn 1020. The horn 1020 is then vibrated to weld theconductive plate member 350 and the positive electrode lead tab 120.

As described above, the notch 125 in the positive electrode lead tab 120and the notch 135 in the negative electrode lead tab 130 are used aslocations to make contact with the anvil 1010 in performing welding bythe ultrasonic welding apparatus.

The battery pack 700 according to the present invention is alsocharacterized in that the position where the conductive plate member 350and the positive electrode lead tab 120 are conductively connected bywelding and the position where the conductive plate member 350 and thenegative electrode lead tab 130 are conductively connected by welding donot overlap as seen in the thickness direction of the conductive platemember 350.

The battery coupling structure 500 can be obtained by welding all thelead tabs inserted through the coupling assisting member 300 to thecorresponding conductive plate members 350 by the foregoing weldingmethod.

FIG. 12 is a diagram showing the battery coupling structure 500 used inthe battery pack 700 according to the embodiment of the presentinvention. FIG. 13 is an exploded perspective view of the batterycoupling structure 500 used in the battery pack 700 according to theembodiment of the present invention. As shown in FIG. 13, it can be seenthat the presence of the guide plates 330 forms the bends (vibrationtransmission ratio changing bends 150) on the respective lead tabs.

FIG. 14 is a front view of the battery coupling structure 500. FIG. 15is a sectional view taken along line A-A shown in FIG. 14. FIG. 16 is aside view of the battery coupling structure 500. FIG. 17 is a sectionalview taken along line B-B shown in FIG. 16.

According to the battery pack 700 of the present invention, a batterypack 700 having light weight, resistant to mechanical vibrations andimpact, and having excellent manufacturability can be provided by usingthe battery coupling structure 500 configured as described above.

According to the method for manufacturing the battery pack 700 of thepresent invention, a battery pack 700 having light weight and resistantto mechanical vibrations and impact can be easily manufactured.

In the present invention, the ultrasonic welding technique is used toweld metal materials such as lead tabs. The application of vibrations tothe lead tabs for the sake of ultrasonic welding has had a problem thatthe vibrations propagate to points where current collector foils and thelead tabs are connected inside the laminate film casings, causing damagesuch as a drop in connectivity at the points.

FIG. 18 is a schematic diagram showing an internal structure of abattery cell 100. Current collector foils 106 are led out from theelectrode stack 102 in the laminate film casing 103, bundled up, andconnected to the positive electrode lead tab 120 (or negative electrodelead tab 130) at the bundled part to form a connection portion 107.

FIG. 19 is a schematic diagram for describing an effect of vibrations inwelding the lead tab and the coupling assisting member 300 on theinternal structure of the battery cell 100. As shown in FIG. 19, thehorn 1020 applies ultrasonic vibrations with the conductive plate member350 and the positive electrode lead tab 120 (or negative electrode leadtab 130) sandwiched between the anvil 1010 and the horn 1020.

A frequency ratio u can be defined as u=f/f_(n), where f_(n) is thenatural frequency of the battery cell 100 and f is the frequency of thehorn 1020. Vibrations transmitted from the horn 1020 to the battery cell100 can be known from a vibration transmission ratio τ.

FIG. 20 shows a relationship between the frequency ratio u and thevibration transmission ratio τ. Referring to FIG. 20, possible patternsof the relationship can be categorized as follows:

Pattern A:

If (frequency ratio u)<1 or 1<(frequency ratio u)<√2, the vibrationtransmission ratio τ is 1 or greater. This shows that the vibrationsapplied from the horn 1020 are amplified when transmitted to theconnection portion 107 of the battery cell 100;

Pattern B:

If (frequency ratio u)=1, the vibration transmission ratio τ isinfinite. This results in a worst-case state where the vibrationsapplied from the horn 1020 are amplified to infinite and applied to theconnection portion 107 of the battery cell 100; and

Pattern C:

If √2<(frequency ratio u), the vibration transmittance ratio τ is lessthan 1. This shows that the vibrations applied from the horn 1020 areattenuated and transmitted to the connection portion 107 of the batterycell 100. If the frequency ratio u is in the range of 2≤(frequency ratiou)≤3, vibrations are known to be sufficiently attenuated for a vibrationisolation effect.

In the welding process of the conductive plate member 350 and the leadtab, the frequency ratio u can enter the category of pattern A orpattern B, depending on the natural frequency f_(n) of the battery cell100 and the frequency f of the horn 1020. The gist of the presentinvention is to bring the vibration transmission ratio τ into thecategory of pattern C by providing the vibration transmission ratiochanging bend 150 on the lead tab.

FIG. 21 is a diagram for describing the concept of changing thevibration transmission ratio by the provision of the vibrationtransmission ratio changing bend 150 on the lead tab. In the presentembodiment, the vibration transmission ratio changing bend 150 isdescribed to be formed by the guiding plate 330 of the couplingassisting member 300. However, the method for forming the vibrationtransmission ratio changing bend 150 on the lead tab is not limited tosuch an example.

As shown in FIG. 21, the formation of the vibration transmission ratiochanging bend 150 on the positive electrode lead tab 120 (or negativeelectrode lead tab 130) changes the natural frequency of the batterycell 100 to f_(n)′. The resulting new frequency ratio u′=f/f_(n)′ canchange the vibration transmission ratio to τ′. The vibrationtransmission ratio changing bend 150 is adjusted so that the newvibration transmission ratio τ′ falls within the category of pattern C.

According to the battery pack 700 of the present invention describedabove, a highly reliable battery pack 700 without a drop in connectivitybetween the current collector foils 106 and the lead tabs (120, 130)inside the laminate film casings 103 can be provided.

According to the method for manufacturing the battery pack 700 of thepresent invention, a highly reliable battery pack 700 without a drop inconnectivity between the current collector foils 106 and the lead tabs(120, 130) inside the laminate film casings 103 can be easilymanufactured.

The battery pack 700 according to the present invention can be obtainedby connecting the power lines 610 and the sense lines 620 to thesubstrate 390 of the battery coupling structure 500 shown in FIGS. 12 to17 via not-shown connectors or the like, and covering the batterycoupling structure 500 with a case 600. FIG. 22 is a diagram showing thebattery pack 700 according to the embodiment of the present invention.

As described above, according to the battery pack of the presentinvention, a battery pack having light weight, resistant to mechanicalvibrations and impact, and having excellent manufacturability can beprovided.

According to the method for manufacturing a battery pack of the presentinvention, a battery pack having light weight and resistant tomechanical vibrations and impact can be easily manufactured.

According to the battery pack of the present invention, a highlyreliable battery pack having excellent manufacturability can beprovided.

According to the method for manufacturing a battery pack of the presentinvention, a highly reliable battery pack can be easily manufactured.

According to the battery pack of the present invention, a highlyreliable battery pack without a drop in connectivity between the currentcollector foils and the lead tabs inside the laminate film casings canbe provided.

According to the method for manufacturing a battery pack of the presentinvention, a highly reliable battery pack without a drop in connectivitybetween the current collector foils and the lead tabs inside thelaminate film casings can be easily manufactured.

INDUSTRIAL APPLICABILITY

Attempts have been made in recent years to use flying objects such as adrone in business and other fields. Since a battery pack mounted on aflying object needs to have high energy density and light weight, itmakes sense to use a battery pack including a battery cell with alaminate film casing. If such a battery pack to be mounted on a flyingobject includes a plurality of battery cells connected to obtain highoutput, the connections need to have high resistance against impact andhigh resistance against vibrations.

However, battery packs according to the conventional technique have hada problem of fragility to impact and vibrations since mechanical fixingmeans such as bolts are used to electrically connect the lead tabs ofthe battery cells. There has also been a problem of increased weight dueto the use of bolts for electrical connection. On the other hand, in thebattery pack according to the present invention, the adjoining batterycells are electrically connected by using the coupling assisting memberincluding the conductive plate member fixing portions, the first slitportions, and the second slit portions. According to the battery pack ofthe present invention, a battery pack having light weight, resistant tomechanical vibrations and impact, and having excellent manufacturabilitycan thus be provided. This provides extremely high industrialapplicability.

EXPLANATION OF REFERENCE SYMBOLS

-   -   100: battery cell    -   102: electrode stack    -   103: laminate film casing    -   105: electrode stacking region    -   106: current collector foil    -   107: connection portion    -   110: battery main body unit    -   111: first end portion    -   112: second end portion    -   113: side end portion    -   120: positive electrode lead tab    -   125: notch    -   130: negative electrode lead tab    -   135: notch    -   150: vibration transmission ratio changing bend    -   200: reinforcing member    -   210: flat plate portion    -   220: rim portion    -   225: handle portion    -   240: protrusion    -   245: latch piece    -   300: coupling assisting member    -   310: frame member    -   320: conductive plate member fixing portion    -   322: conductive plate member sandwiching portion    -   325: conductive plate member latch portion    -   330: guide plate    -   340: recessed guide (guide portion)    -   350: conductive plate member    -   351: first main surface    -   352: second main surface    -   353: notch    -   355: slit portion    -   357: terminal piece    -   361: first slit portion    -   362: second slit portion    -   390: substrate    -   393: through hole    -   500: battery coupling structure    -   600: case    -   610: power line    -   620: sense line    -   700: battery pack    -   1010: anvil    -   1020: horn

The invention claimed is:
 1. A battery pack comprising a stack of aplurality of battery cells that each include a positive electrode leadtab and a negative electrode lead tab led out of a laminate film casingin a same direction, and a coupling assisting member that assists inelectrically connecting adjoining battery cells, wherein: a notch isformed in each of the positive and negative electrode lead tabs of eachbattery cell of the plurality of battery cells, and the couplingassisting member of each battery cell of the plurality of battery cellsincludes: a conductive plate member fixing portion that fixes aconductive plate member having a first main surface and a second mainsurface in a front-to-back relationship with the first main surface, afirst slit portion provided on the first main surface side of theconductive plate member, and a second slit portion provided on thesecond main surface side of the conductive plate member; wherein eitherone of the positive and negative electrode lead tabs of one battery cellis inserted through the first slit portion thereof and is conductivelyconnected to the first main surface of the conductive plate memberthereof; an electrode lead tab, having a polarity different from that ofthe electrode lead tab of the one battery cell which is inserted throughthe first slit portion thereof, of another battery cell adjoining theone battery cell, is inserted through the second slit portion of theanother battery cell and is conductively connected to the second mainsurface of the conductive plate member of the another battery cell; aposition where the one of the positive and negative electrode lead tabsof the one battery cell inserted through the first slit portion thereofand conductively connected to the first main surface of the conductiveplate member thereof and a position where the electrode lead tab of theadjoining another battery cell, having the polarity different from thatof the electrode lead tab of the one battery cell, and which is insertedthrough the second slit portion of the another battery cell and which isconductively connected to the second main surface of the conductiveplate member of the another battery cell, do not overlap as seen in athickness direction of the conductive plate member of the anotherbattery cell.
 2. The battery pack according to claim 1, wherein thecoupling assisting member of each battery cell of the plurality ofbattery cells includes a guide plate such that, when an electrode leadtab of a battery cell of the plurality of battery cells is insertedthrough the first slit portion or the second slit portion thereof, thecoupling assisting member guides an end of the electrode lead tab towardthe first slit portion or the second slit portion.
 3. The battery packaccording to claim 1, wherein the conductive plate member fixing portionof the coupling assisting member of each battery cell of the pluralityof battery cells includes a conductive plate member sandwiching portionthat sandwiches the conductive plate member thereof.
 4. The battery packaccording to claim 1, wherein the conductive plate member fixing portionof the coupling assisting member of each battery cell of the pluralityof battery cells includes a conductive plate member latch portion thatlatches the conductive plate member thereof.
 5. The battery packaccording to claim 4, wherein in each battery cell of the plurality ofbattery cells, the conductive plate member includes a notch for theconductive plate member latch portion to be engaged with.
 6. The batterypack according to claim 1, wherein in each battery cell of the pluralityof battery cells, a terminal piece is formed on the conductive platemember.
 7. The battery pack according to claim 6, wherein in eachbattery cell of the plurality of battery cells, a substrate having athrough hole for the terminal piece to run through is placed on thecoupling assisting member.
 8. A method for manufacturing a battery packincluding a stack of a plurality of battery cells that each include apositive electrode lead tab and a negative electrode lead tab led out ofa laminate film casing in a same direction, and a coupling assistingmember that assists in electrically connecting adjoining battery cells,the battery pack being configured such that a notch is formed in each ofthe positive and negative electrode lead tabs of each battery cell ofthe plurality of battery cells, and the coupling assisting member ofeach battery cell of the plurality of battery cells including aconductive plate member fixing portion that fixes a conductive platemember having a first main surface and a second main surface in afront-to-back relationship with the first main surface, a first slitportion provided on the first main surface side of the conductive platemember, and a second slit portion provided on the second main surfaceside of the conductive plate member, the method comprising: insertingeither one of the positive and negative electrode lead tabs of onebattery cell into the first slit portion thereof and conductivelyconnecting the electrode lead tab to the first main surface of theconductive plate member thereof; and inserting an electrode lead tab ofanother battery cell adjoining the one battery cell, the electrode leadtab of the another battery cell having a polarity different from that ofthe electrode lead tab of the one battery cell, into the second slitportion of the another battery cell and conductively connecting theelectrode lead tab to the second main surface of the conductive platemember of the another battery cell, wherein, a position where the one ofthe positive and negative electrode lead tabs of the one battery cellinserted through the first slit portion thereof and conductivelyconnected to the first main surface of the conductive plate memberthereof and a position where the electrode lead tab of the adjoininganother battery cell, having the polarity different from that of theelectrode lead tab of the one battery cell, and which is insertedthrough the second slit portion of the another battery cell and which isconductively connected to the second main surface of the conductiveplate member of the another battery cell, do not overlap as seen in athickness direction of the conductive plate member of the anotherbattery cell.
 9. A battery pack comprising a stack of a plurality ofbattery cells that each include a positive electrode lead tab and anegative electrode lead tab led out of a laminate film casing in a samedirection, and a coupling assisting member that assists in electricallyconnecting adjoining battery cells, wherein: a notch is formed in eachof the positive and negative electrode lead tabs of each battery cell ofthe plurality of battery cells, and the coupling assisting member ofeach battery cell of the plurality of battery cells includes: aconductive plate member fixing portion that fixes a conductive platemember having a first main surface and a second main surface in afront-to-back relationship with the first main surface, wherein eitherone of the positive and negative electrode lead tabs of one battery cellof the plurality of battery cells is conductively connected to the firstmain surface of the conductive plate member of the one battery cell; anelectrode lead tab, having a polarity different from that of theelectrode lead tab of the one battery cell which is conductivelyconnected to the first main surface of the conductive plate member ofthe one battery cell, of another battery cell adjoining the one batterycell, is conductively connected to the second main surface of theconductive plate member of the another battery cell, and a positionwhere the one of the positive and negative electrode lead tabs of theone battery cell conductively connected to the first main surface of theconductive plate member of the one battery cell and a position where theelectrode lead tab of the adjoining another battery cell having thepolarity different from that of the electrode lead tab of the onebattery cell, which is conductively connected to the second main surfaceof the conductive plate member of the another battery cell do notoverlap as seen in a thickness direction of the conductive plate memberof the another battery cell.